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Large ring laser gyros are regarded as suitable sensors for precise monitoring of the Earth’s rotation. Their long-term stability, high sensitivity, and mechanical properties suggest themselves for potential terrestrial deployment, such as Universal Time (UT1), Length of Days (LOD), Geophysics, etc. This inertial technology based on Sagnac interferometers measure any non-reciprocal effect which gives rise to a difference of optical path lengths between forward-propagating laser beams and the counter-propagating within the cavity. Differing from their cousins used in navigation, large ring lasers is usually a heterolithic optical cavity composed of four independent reflector components s to avoid employing large whole Zerodur. Comparing with other UT1 measuring technologies, large ring lasers has characteristics of higher resolution and good real-time, which is highly complementary to VLBI observation technology. In order to meet the measurement of UT1 error less than 1ms/day to coordinate with VLBI, the resolution of ultra-stable laser gyros must be better than 10e-13rad/s. The geometric stability of heterolithic ring cavity is demanded stringently. We simulated the intrinsic relationship between geometric deformation and scale factor of optical cavity. The influence of temperature on geometric deformation has been analyzed and the temperature compensation strategy is proposed. The temperature field distribution of the laser gyro is approximately evaluated by measuring the temperature network of some specific points.
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